When I put my wipers on intermittant, they are really slow and/or the blades just stop half way or shake their way across the screen. This does not happen if the wipers are on normal sequence. After the wipers have been operating for a while, the intermittant switch works fine.
Any ideas as to the cause would be grateful, is it the switch or the wiper motor?
Thanks.

i take it this must be a late model car or truck..... anyway my 84 chevy suburban did the same thing & what i have found is the circuit board in the wiper mtr is going bad. the only thing i could find to fix it was replace the mtr..

but then it may even be the switch in the column need cleaning or replaced.....joe

When I put my wipers on intermittent, they are really slow and/or the blades just stop half way or shake their way across the screen. This does not happen if the wipers are on normal sequence. After the wipers have been operating for a while, the intermittent switch works fine.
Any ideas as to the cause would be grateful, is it the switch or the wiper motor?
Thanks.

If you can give us the year make and model of whatever you are working on we might be able to help.

My knowledge of electrical stuff is sfa, but I am curious as to why all wipers do not just have an on/off switch and a rheostat to vary the speed as required instead of having just set speeds. Would this require different types of motors or far greater expense.

You might also want to check the linkages (and in some cases, motor transmission) For lubrication..and Wipers For "Hard Blades".

You may have issues with the linkages or Blades that the slow speed setting can't overcome (excessive drag on the motor) until it "Warms up a bit" or the blades soften up in the rain..Excessive Downward force on the wiper arms can cause this too..

A Rheostat Is a very ineffective way to control motor speed anymore..In it's day it was OK, but was subject to Excessive heat (as it varied the motor speeds) and was subject to mechanically falling apart, Dirt or wear spots on the most common used setting, or the Center wiper losing tension under load..It required more space to mount it (away from stuff that would be effected by heat, and because it was physically larger).

With the introduction of Buffered semiconductors (low current signal to drive high current devices) The problems of motor speed control have almost been eliminated, no mechanical parts to wear out, Less heat generated,Less space required to mount the componet.Plus it makes it easier to interface to other options like moisture detectors and the like.

Multi tap or wound motors achieve the same principle but are far more costly to produce than a single tap motor..So from a manufacturer's point of view, that answer is self evident..

GM for years, used a series of 3 Resistors on their heater motor speed control to achieve different speed settings, It was a weak point in the system as they would fail quite a bit..along with the controller switch (works well on High only..)

You raise quite an interesting point. Seems to me it would be pretty easy to use some transistors and a microcontroller to send pulses, thus controlling the motor's speed (this is how electric forklifts and any electric motor's speed is varied, the rheostat idea is inefficient in comparison).

However, would it be more annoying to have the wipers wipe once in X amount of time, or to have the blades slooooowwwly creep across the windshield? I can see this being bad, as I love adjusting the vacuum wipers in my rambler to the beat of whatever is on the radio at the time. I can see it now, accidents all over the country because soccer mom was messing with the wipers to make them swish to the beat of Rob Thomas songs and didn't see that the light turned red up ahead......

You raise quite an interesting point. Seems to me it would be pretty easy to use some transistors and a microcontroller to send pulses, thus controlling the motor's speed (this is how electric forklifts and any electric motor's speed is varied, the rheostat idea is inefficient in comparison).

However, would it be more annoying to have the wipers wipe once in X amount of time, or to have the blades slooooowwwly creep across the windshield? I can see this being bad, as I love adjusting the vacuum wipers in my rambler to the beat of whatever is on the radio at the time. I can see it now, accidents all over the country because soccer mom was messing with the wipers to make them swish to the beat of Rob Thomas songs and didn't see that the light turned red up ahead......

Doc here,

Pulse Width modulation is an excellent way to control motor speed. (and other applications as well) Simply because It's Duty Cycle is less than Half of the peak of an analog voltage (If your doing it right.. )

You Can control a Motor at the same speed and torque with pulse width modulation at half the rate of power consumption..(simply because the Pulse is off 50% of the time..) and your source Current (the battery) will last twice as long as it would straight analog, and do the same amount of work..Since the motor is analog technology..It doesn't even see the "Off" portion of the duty cycle..because the Controller is operating at a much higher frequency than would effect an analog device....

By varying the frequency rate or modulation width, you gain speed control, while still conserving power at a rate much more acceptable than analog..

Couple a Pulse width modulator with a bank of hefty SCR's, and then into the most efficient motor you can find.. and you have a perfect platform For an EV or tow motor..Speed controller...

I built an EV back in the 70's ... It was a Volkswagen Pan (modified like a sand-rail frame to reduce weight) and a fiberglass gull wing kit body...

Built the Controller myself, (since that technology was in it infancy then..) as a microprocessor based pulse width modulator..(also new technology then..)You COULD actually program in consumption rates, speed and torque limits with an umbilical keyboard in the passenger compartment..

The motor was a 4cm..something or another..I think 70..but can't remember..But the motor wasn't very efficient, and was a starter motor off an F100 fighter..a 24/48 volt motor..run at 72 volts (full load condition..)

The car had 12 , 6 volt deep cycle marine batteries weighing in at about a whopping 1300 pounds....(also not very efficient...)

I had machined, an adapter plate for the motor and clutch system (sans ring gear teeth)to the transaxel that coupled the two units together..at the input shaft of the transaxel..thus it operated as a standard VW to drive it..4 forward , 1 reverse..and a regular clutch..

Anyway..The Short story..It was not the fastest thing off the line..The paperboy could beat it off the line even giving me a 1 second RT handicap..

However..once you were in second or third the car operated comparable to an internal combustion engine vehicle, without all the noise..It did have a top speed of about 70 mph...on flat , level ground, and you could get about an hour run time out of the battery's before having to recharge..depending on how you drove it..

After Several phone calls (computers were also in their infancy then.. ) To George Kaylor..(EV Guru at the time..) in Santa Rosa, We came to the conclusion that until such time as a better, higher current, longer life, lightweight battery bank system, and a charging system that could overcome the laws of physics were invented..and more efficient motors were available...The TRUE EV would be a passing phase...nothing more than a hobby..And the Car ended up as "Parts" by the early 80's!

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